Roasting the flavorings: On an ungreased griddle or heavy skillet set over medium, roast the garlic cloves, turning occasionally, until soft (they will blacken in spots), about 15 minutes. Cool and peel. While the garlic is roasting, lay the onion out on a small square of foil, set on the griddle and let sear, brown and soften, about 5 minutes on each side. Roast the tomatoes on a baking sheet set 4 inches below a very hot broiler until blackened in spots and soft, about 6 minutes; flip and roast the other side. Cool and peel, collecting all the juices with the tomatoes.
The sauce: Combine all the roasted ingredients in a food processor or blender, along with the pepper, cloves and 1/4 cup water. Process to a medium-smooth puree. In a very large skillet, heat the oil over medium-high heat. When hot enough to make a drip of the puree sizzle noisily, add it all at once. Stir for several minutes as the mixture sears and darkens then reduce the heat to medium-low and continue to cook, stirring regularly, until very thick, about 5 minutes. A tablespoon at a time, stir in the Chipotle Seasoning Salsa (or chopped chipotle), tasting until the thick salsa suits your own penchant for spiciness. Taste, season with salt and remove from the heat.
The shrimp: Peel and devein the shrimp, leaving the final joint and the tail intact. Return the skillet with the sauce to medium-high heat. Add the shrimp, then slowly stir and turn for about 3 to 4 minutes, until the shrimp are just cooked through. Season with salt if needed. Serve the shrimp with the rice. Garnish with cilantro.
Recipe adapted from Rick Bayless's Mexican Kitchen, by Rick Bayless, published by Scribner, 1996